1. Field of the Invention
This disclosure relates to a passive optical pen, and more particularly to a passive optical pen for using with a display device.
2. Description of the Prior Art
Nowadays, display devices with touch panels have been widely used as a medium of data communication in each scope of consuming electric products, such as personal digital assistants (PDAs), mobile phones, notebook computers, tablet PCs and other wireless portable products. For a touch panel, the functions of inputting and outputting signals are integrated within one medium (screen). The requirement of display devices for miniaturization has pushed touch panels to become one of the most important user input systems.
Please refer to FIG. 1. FIG. 1 is a schematic diagram of a traditional user input system 100 having an active optical pen 112. The traditional user input system 100 includes a touch panel 102 and an active optical pen 112. The touch panel 102 is usually attached to a surface of a display panel 120 by an adhesive layer 122, and includes a glass substrate 104, a detecting layer 106 and a protecting layer 108. The detecting layer 106 has a plurality of photo sensors and a photo-detecting circuit (not shown in the figure) for detecting light propagated from the outside. Meanwhile, the active optical pen 112 includes a light source 114 to radiate light toward the touch panel 102. Since the detecting layer 106 of the touch panel 102 could sense positions of the light radiated from the active optical pen 112, a user can interact with the user input system 100 utilizing the active optical pen 112.
Because the prior art active optical pen 112 must include a light source 114 to radiate light, it is necessary for the active optical pen 112 to couple with a power source by a wire, or to include a battery inside. Therefore, the prior art active optical pen 112 has the disadvantages listed as follows. First, the active optical pen 112 is heavy and cumbersome, so miniaturization of the active optical pen 112 is limited. The traditional user input system 100 including a cumbersome active optical pen 112 is inconvenient for portable products. Secondly, the prime cost of the active optical pen 112 including a light source 114 and a power system is expensive. Thirdly, there is further a power consumption of the active optical pen 112 during the input operation.